Because they are forced to squeeze so much of their humour from certain limited character traits and situations, sitcoms tend to get boring relatively quickly. The creators of the best of them realise this. The Office (UK), Extras and Fawlty Towers, three of television's greatest comedic achievements, featured just 12
Greg Bruce on The Good Place: A good thing

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Kristen Bell and Ted Danson in The Good Place.
Schur had to ask himself whether viewers would relate to the concept of the second season as well as they had to the first, which had been a critical success and at least enough of a commercial success for a second season. (Netflix doesn't release viewer numbers so we can never be sure how commercially successful any of their shows are.)
This act is just one of many brave things about the show, including the fact that its characters spend a surprising amount of time having actual classroom lessons in moral philosophy, which are things that even professional philosophers would define as "not really entertainment".
More or less a whole episode in season two, for instance, is devoted to "The Trolley Problem", typically the basis of lecture one in Moral Philosophy 101. Watching it, you can almost hear philosophy professors around the world embedding the video in their PowerPoint presentations.
Philosophy professors and self-help authors have long understood that "What does it mean to live a good life?" is the most important question humans can ask themselves. Generally we use TV as a way to avoid asking it, so it's an act of severe subversiveness to get us asking and watching simultaneously.
It's a great achievement and a great show. It can't last forever, but what ever does?
Oh, yes. The Simpsons.